So far, I only find one way to happiness: to have everything. A man is happy if he has everything. The condition is still sounds as everything is the complement of nothing. A man is happy if he needs nothing which implies he has everything.

But, there are still 3 ways interpreting “to have everything” :

A man could earn every atomic entity in this universe, which obviously is still impossible in every means possible.

A man thinks he has everything, which implies a man who thinks he has everything is happy.

A man has what he thinks is everything, which implies a man who has what he thinks is everything is happy.

The point lies in way 2 and 3 is in the word “think”. A man is just what he thinks he is.
In other words, A man is happy if he thinks he is happy in either way he thinks he has everything or he has what he thinks is everything.